Tool and method of making the same



K. SCHROTER El AL 2,019,934

TOOL AND METHOD OF MAKING THE SAME Filed May 29, 1930 Nov. 5, 1935.

fin/ea METAL Auo 801.051? Toast! METAL Si ica/M436 Patented Nov. 5, 1935 PATENT OFFICE TOOL AND METHOD OF MAKING THE SAME Karl Schriiter, Berlin-Lichtenberg,

Wolil, Berlin, Ge

and Hans assirnors to Fried.

Krupp Aktiengesellschait, Essen-on-the-Ruhr,

Germany Application May 29, 1930, Serial No. 457,514

BIG

Claims.

In manufacturing tools nowadays frequently hard metal alloys are used which in the most cases consist of carbids oi tungsten or molybdenum, in some cases with addition of more easily melting auxiliary metals such as cobalt, nickel or iron. As a rule, tools of this type are not manufactured throughout from the hard metal alloy, but a shape made from a hard metal alloy and forming the tool proper is soldered by means of copper or brass on a carrier which consists of steel or ordinary iron and forms a stem, disk or the like.

With such soldered tools sometimes fine cracks arise in the shaped body of hard metal alloy whichcracks begin immediately at the soldering joint and extend in aflat curvature. Probably these cracks are due to the different coeflicients of expansion of the hard metal alloy and of the metal the carrier consists of. For, while all hard metal alloys on the market possess an extraordinarily low coeflicient oi. expansion (about 510-) with the usual carrier metals, that is steel or iron, this coeflicient is about twice that of the former. I

In order to take up the difierences of expansion and to avoid thus formation of noxious cracks in the hard metal bodies, according to the invenvention a tough metal blade which has the same or approximately the same coemcient of expansion as the hard metal alloy, for instance a blade of molybdenum, is put on the place whereon the hard metal body is to be soldered, whereupon the soldering itself is carried out in the usual manner, for instance by means of copper or brass. Owing to their toughness metal blades of this kind on the one hand are capable of taking up the stresses arising in soldering, but, on the other hand, they do not transmit these stresses to the hard metal body owing to their coeflicient of expansion being approximately or exactly the same as that of the hard metal alloy.

Soldering is then advantageously proceeded with by applying to the carrier, for instance a stem, a copper bladecovered with borax, then a molybdenum blade, then another copper blade and, finally, the shaped body oi hard metal alloy, whereupon the whole is heated in the electric furnace to about 1100 degrees C. The soldered places neither immediately after soldering nor after long use oi'the tool show any cracks and not even when the hard metal alloys the shaped bodies consist of have a particular tendency to cracking. I

The drawing shows a tool made in accordance ermany November 6, 1929 with the invention and illustrates the manner in which the tool is built up. Fig. 1 is an exploded view of the parts of which the tool is composed, in side elevation, and Fig. 2 is a side elevation of the finished tool.

In the drawing I represents a stem of a lathe tool, which may be composed of steel or ordinary iron, the stem being notched out at one end to receive the hard metal tip. In the notch of the stem are laid, first a copper blade covered 10 with borax, then a blade of tough metal, for instance of molybdenum or soft steel, then another copper blade, and, finally, the shaped body of hard metal alloy. The manner in which the parts are assembled is, of course, immaterial, so 15 long as they finally arrive in the positions indicated above. When they are all assembled they are heated in the electric furnace to about 1100" 0., whereby the parts become soldered together.

In'lieu of the molybdenum blade a blade of nickel iron, chromium-nickel or of any other alloy can be used the coefllcient of expansion of which approximately corresponds to that of the hard metal alloy. To facilitate soldering, the metal blades to be applied to the soldering place 25 may be covered previous to being applied with a soldering metal, such as copper, and with a flux. Metal blades prepared in this manner can conveniently be marketed and kept in stock as ready-made soldering inserts. 30

"We claim:-

1. The method of manufacturing hard metal tools composed of a carrier made from steel or iron and a body of hard metal alloy forming the tool proper having a coeflicient of expansion materially lower than the carrier metal, consisting in interposing between said carrier and body a blade of tough metal covered on both sides with soldering metal and the coeflicient of expansion of which at least approximately corresponds to that of said body, and uniting these three parts by soldering.

2. The method of manufacturing hard metal tools composed of a carrier made from steel or iron and a body 01 hard metal alloy forming the tool proper, consisting in applying on said carrier a blade of copper covered with borax, then a blade of molybdenum thereon, then again a blade of copper covered with borax, and there on said hard metal body, and uniting this pile of parts by soldering.

3. A tool comprising a carrier of steel or iron, 8. body of a hard metal alloy forming the bit of the tool and having a coeflicient of expansion decidedly lower than that of said carrier, and an 10 an intermediate hater-mediate, layer of a tough metal between said carrier and body having a coemcient or expansion at least approximately the same as said hardmet'aY-aIlQy body, said parts being united Aftool comprising a carrierot steel or iron,

a 'body ofa hard metal alloy forming the bit of thjtodl and having a coeilicient of expansion decidedly difierent from that or said carrier, and layer of molybdenum between said carrier and body having a coeflicient of expansion at least approximatelyvthe same as said hard metal alloy body, said parts being united by solder.

HANS WOLFF. 

